exercise stress test
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EXERCISE STRESS TEST. Physiology and Protocol, Indications and Contraindications DN. Essential ET Terminology Performance of the E S T Assess Exercise Test Responses Interpretation Of The Exercise Stress Test. - PowerPoint PPT PresentationTRANSCRIPT
EXERCISE STRESS TEST Physiology and Protocol,
Indications and Contraindications
DN
• Essential ET Terminology
• Performance of the E S T
• Assess Exercise Test Responses
• Interpretation Of The Exercise Stress Test
Exercise Test Terminology
• Vo2max
• METs
• Myocardial Oxygen Consumption
Maximal Oxygen Uptake (VO2max)
• Greatest amount of oxygen an individual utilizes with maximal exercise (ml O2 /kg/ min)
• “Gold Standard” for cardiorespiratory fitness
• Fick EquationVo2max = (HRmax x SVmax) x (CaO2max -
CvO2max)
VO2max = (HRmax X SVmax) X (CaO2max - CvO2max)Genetic Factors (Heart Size)Conditioning Factors Contractility/Afterload/PreloadDisease Factors Wall Motion/Ventricular Fn, Valve Stenosis or Regur
Skeletal Muscles• Aerobic Enzymes• Fiber Type• Muscle Disease• Cap density
PaO2
Hgb [ ]
SaO2
DiffusionVentilationPerfusion
FICK EQUATION
(220 - Age)
Sinus Node Dysfunction
Drugs (e.g., B - blockers)
MET
•Metabolic Equivalent Term
•1 MET = "Basal" aerobic oxygen consumption to stay alive = 3.5 ml O2 /Kg/min
• inf- thyroid status, post exercise, obesity, disease states
MET Values
• 1 MET = "Basal" = 3.5 ml O2 /Kg/min
• 2 METs = 2 mph on level
• 4 METs = 4 mph on level
• < 5METs = Poor prognosis if < 65;
10 METs = prognosis with med therapy =
CABG
13 METs = Excellent prognosis
16 METs = Aerobic master athlete
Calculation of METs on the Treadmill
METs = Speed x [0.1 + (Grade x 1.8)] + 3.5
3.5
Calcul automatically by device
Speed in meters/minute = MPH x 26.8
Grade expressed as a fraction
Myocardial (MO2) Accurate measurement - cardiac catheterization
Coronary Flow x Coronary (a – v)O2 diff
HR, SBP, LVEDV, CONTRACTILITY, WALL THICKNESS
.
Myocardial Oxygen Consumption
• Indirectly measured as the “Double Product”
• “Double Product” = HR x SBP
– A normal value is greater than 20,000 – 25,000
– < 20,000 is low heart work load– > 29,000 indicates high heart work load
• Angina & ST↓occur at the same DP for an individual
Types of Exercise1. Isometric (Static)
-weight-lifting -pressure work for heart, limited
cardiac output
2. Isotonic (Dynamic) -walking, running, swimming, cycling -Flow work for heart -↑CO,↓ TPR
3. Mixed
Exercise physiology
• Sympathetic activation• Parasympathetic withdrawal• Vasoconstriction, except in-
– Exercising muscles– Cerebral circulation – Coronary circulation
• ↑norepinephrine and renin
Exercise physiology
• ↑ventri contractility
• ↑O2 extraction(upto 3)
• ↓peripheral resistance
• ↑SBP,MBP,PP
• DBP –no significant change
• Pulm vasc bed can accommodate 6 fold CO
• CO - ↑ 4-6 times
Exercise physiology
Isotonic exercise(cardiac output)• Early phase- SV+HR• Late phase-HR
• peak oxygen consumption- age, sex, & training level of the person performing the exercise
• The plateau in peak oxygen consumption- Vo2 max
• Vo2 max is limited by
1)the ability to del O2 to sk. muscles 2) muscle oxidative capacity .
Oxygenconsumption(liters/min)
Work rate (watts)
V02 peak
(VO2max)
• dynamic exercise- ventilation increases linearly over the mild to moderate range, then > rapidly in intense exercise
• workload at which rapid ventilation occures is called the ventilatory breakpoint (together with lactate threshold)
Respiration during exercise
Lactate acidifies the blood, driving off CO2 and increasing ventilatory rate
BP rise in exercise
• (SBP) ↑up to 150-170 mm Hg during dynamic exercise; diastolic rarely alters
• isometric - SBP may ≥250 mmHg, and DBP can reach 180
Bloodlacticacid(mM)
Relative work rate (% V02 max)
Intense exercise Glycolysis>aerobic metabolism ↑ blood lactate
Lactate threshold; endurance estimation
Age Pred Max HR
• APMHR=220 - age in years\• APMHR=200-1/2 age
• MHR ↓ with age• Lower/higher than actual value(+/_12beats)• Not used as an indicator of max exertion in
EST/ Indi to terminate test
.
Post exercise phase
• Vagal reactivation -Imp-cardiac decceleration mech
• ↑in well trained athletes
• Blunted in CCF
ENERGY REQ ACTIVITY
1 MET TAKING CARE OF SELFWALKING INDOORSWALK AT 2-3 mph
4 METS LIGHT WORK AROUND THE HOUSEWALKING AT 3-4 mph
>4-<10 METS CLIMB 1 FLIGHT OF STAIRS/UP HILLWALK>4 mph, SHORT RUNNINGSCRUBBING FLOOR,MOVING FURNITURE
>10 METS RUNNING> 6-7 mphHEAVY LABOURSWIMMING,FOOTBALL
Exercise Stress Testing
• Pathophysiology:
– At rest- adequate coronary blood flow– with exercise-supply\demand mismatch -ST
segment changes
– 70-80%occlusion - detection by EST
– Sign CAD can exist with a -VE Exercise Stress Test.
Treadmill protocol EST- stand protocols to progressively ↑ cardiovascular
work load in a uniform and reproducible way
• Bruce protocol• Naughton protocol• Weber protocol• ACIP(asymptomatic cardiac ischemia pilot)• Modified ACIP
The Bruce protocol• 1949 by Robert A. Bruce,
considered the “father of exercise physiology”.
• Published as a standardized protocol in 1963.
• gold-standard for detection of myocardial ischemia when risk stratification is necessary.
BRUCE Protocol
Stage Time (min) M/hr Slope
1 0 1.7 10%
2 3 2.5 12%
3 6 3.4 14%
4 9 4.2 16%
5 12 5.0 18%
6 15 5.5 20%
Peak Vo2 is the same regardless of the protocol useddiff – rate at which it is achieved
PROTOCOL USES COMMENTS
BRUCE Normally used large↑Vo2 bet stages\running≥st 3
NAUGHTON&WEBER Limited ex tolerance-CCF 1-2 min stages\1 MET increment
ACIP Established CAD 2 min stages\> linear ↑ in HR & Vo2
MOD-ACIP Short elderly individuals
Procedure
• Standard 12 lead ECG- leads
• Torso ECG + BP– Supine and Sitting / standing
• HR ,BP ,ECG– Before,after,stage – Onset of ischemic response– Each min recovery(5-10 mints)
Procedure- Lead systems
• Mason-Liker modification-extremity electrodes moved to torso 2 ↓ motion artifacts
– RAD– ↑inf lead voltage– Loss of inf lead q– New Q in AVL
Contraindications to Exercise Testing
Absolute• A/c MI (< 2 d)• High-risk unstable angina• Uncontrolled cardiac arrhythmias causing
symptoms or hemo compromise• Symptomatic severe AS• Uncontrolled symptomatic CCF• Acute pulmonary embolus or pulmonary
infarction• A/c myocarditis or pericarditis• A/c Ao dissection
Contraindications to Exercise Testing
Relative• LMCA stenosis• Mod- stenotic VHD• Electrolyte abnormalities• Sev HTN• Tachyarrhythmias or bradyarrhythmias• HOCM and other outflow tract obstructions• Mental or physical impairment leading to
inability to exercise adequately• High-degree AV block
SAFETY & RISKS
In nonselected pat pop-mortality- .01% -morbidity-.05%In k/c CAD- 1 C.arrest/59000 person hours -AMI in 1.4 / 10000 testsArrythmias-AF-Mc-9/10,000 tests -VT-6/10,000 tests -VF- .6/10,000 tests
Deaths& MI estimated occur in 1 of 25000 tests
The post test probability is proportional to the pretest probability
To diagnose, test sensitivity ,specificity& prevalence in the population being tested req
Bayes' theorem A theory of probability
• Sensitivity- a person with the disease having a positive test.
• Specificity-person without the disease having a negative test.
• Prevalence- % in the population having
disease.
Pretest Probability
• Based on the pat's h/o ( age, gender, chest pain ), phy ex and initial testing, and the clinician's experience.
• Typical or definite angina →pretest probability high - test result does not dramatically change the probability.
• Diag power maximal when the pretest probability is intermediate-30-70%
Classification of chest pain
• Typical angina
• Atypical angina
• Noncardiac chest pain
1. Substernal chest discomfort with characterstic quality and duration
2. Provoked by exertion or emotional stress
3. Relieved by rest or NTG
Meets 2 of the above characteristics
Meets one or none of the typical characteristics
Pre Test Probability of Coronary Disease by Symptoms, Gender and Age
Age Gender Typical/DefiniteAngina Pectoris
Atypical/ProbableAngina Pectoris
Non-Anginal
Chest Pain
Asymptomatic
30-39 Males Intermediate Intermediate low (<10%) Very low (<5%)
30-39 Females Intermediate Very Low (<5%) Very low Very low
40-49 Males High (>90%) Intermediate Intermediate low
40-49 Females Intermediate Low Very low Very low
50-59 Males High (>90%) Intermediate Intermediate Low
50-59 Females Intermediate Intermediate Low Very low
60-69 Males High Intermediate Intermediate Low
60-69 Females High Intermediate Intermediate Low
High = >90% Intermediate = 10-90% Low = <10% Very Low = <5%
INTERMEDIATE CATEGORYAGE GROUP GENDER & SYMPTOMS
30-39 YEARS M& F + TYPICAL ANGINA M + ATYPICAL/ PROBABLE ANGINA
40-49 YEARS F + TYPICAL ANGINAM + ATYPICAL/ NON ANGINAL CP
50-59 YEARS F+ TYPICAL ANGINAM&F + ATYPICAL NAGINAM+ NON ACP
60-69 YEARS M& F+ ATYPICAL/PROB ANGINAM&F + NACP
E T TO DIAGNOSE OBSTRUCTIVE CAD
Class I• Adult (including RBBB or <1 mm of resting
ST↓) with intermed pretest probability of CAD
Class IIa• Patients with vasospastic angina.
E T TO DIAGNOSE OBSTRUCTIVE CAD
Class IIb1. Patients - high pretest probability of CAD 2. Patients - low pretest probability of CAD 3. Patients with <1 mm of baseline ST ↓and on digoxin.4. Patients with LVH and <1 mm baseline ST ↓.
Class III1. Patients with the following baseline ECG abnormalities:
• Pre-excitation syndrome• Electronically paced ventricular rhythm• >1 mm of resting ST depression• Complete LBBB
EST SENSITIVITY SPECIFICITY
OVERALL 68% 77%
SVD(LAD>RAD>LCX) 25-71%
MULTIVESSEL DIS 81% 66%
LMCA/3-VD 86% 53%
Exercise Testing in Asymptomatic PersonsWithout Known CAD
Class I • None.
Class IIa• Evaluation of asymP DM pts - plan to start vigorous exercise ( C)
Class IIb• 1. Eval of pts with multiple risk factors - guide to risk-reduction therapy.• 2. Eval of asymptomatic men > 45 yrs and women >55 yrs: Plan to start vigorous exercise Involved in occupations which impact public safety High risk for CAD(e.g., PVOD and CRF)Class III• Routine screening of asymptomatic
RISK ASSESS AND PROGIN PAT WITH SYMP OR APRIOR HISTORY OF CAD
Class I 1. Initial evalu with susp/known CAD +/- RBBB or <1 mm of
resting ST Depression 2.Susp/ known CAD, previously evaluated-+ signi change in
clinical status nw 3. Low-risk UA pts >8 to 12 hrs & free of active
ischemia/CCF 4. Intermed-risk UApts > 2 to 3 days & no active ischemia/
CCFClass IIa Intermed-risk UA pts – initial markers (N),rpt ECG –no signi
change, and markers >6-12 hrs (N) & no other evidence of ischemia during observation.
AFTER MYOCARDIAL INFARCTION
Class I• 1. Before discharge (submaximal --4 to 6 days).• 2. Early after discharge (symptom limited --14 to 21
days).• 3. Late after discharge if the early exercise test was
submaximal (symptom limited --3 to 6 weeks).
Class IIa• After discharge as part of cardiac rehabilitation in
patients who have undergone coronary revascularization.
AFTER MYOCARDIAL INFARCTION
Class IIb1. Patients with the following ECG abnormalities:• • Complete LBBB• • Pre-excit synd• • LVH• • Dig therapy• • >1 mm of resting ST-segment dep• • paced ventricular rhythm2. Periodic monitoring in patients who continue to participate in exercise
training or cardiac rehabilitation.Class III1. Severe comorbidity likely to limit life expectancy and/or candidacy for
revascularization.2. any time to eval pts with AMI with uncompensated CCF, arrhythmia, or
noncardiac exercise limiting conditions. 3. Before discharge to evaluate pts who have already been selected for, or
have undergone, cardiac cath. .
Submaximal protocols • predetermined end point, often a peak HR
120 bpm, or 70% predicted max HR or peak MET – 5
Symptom-limited tests • to continue till signs or sympt needing
termination (i.e., angina, fatigue, ≥ 2 mm of ST↓,v. arrhy, or ≥10-mm Hg drop in SBP from the resting blood pressure)
• The incidence of fatal cardiac events(inclu fatal MI & cardiac rupture)-- 0.03%
• Nonfatal MI and successfully resuscitated cardiac arrest -- 0.09%
• Complex arrhythmias, including VT --1.4%.
• Symptom-limited protocols have an event rate that is 1.9 times that of submaximal tests
High risk predischarge Present Absent
Cardiac cath strategy 2 strategy3
symp lim EST(14-21d) sub max (4-7d)
Symp lim EST(14-21 days) Markedly ab mildly ab negative
Card cath Ex imaging
Reversible ischemia no rev ischemia
Med Rx
Sub max (4-7 days)
Markedly ab mildly ab negative
Ex imaging
Rev ischemia no rev isch
symp lim ex(3-6wks)
card cath markedly ab mildly ab negative
rev isch no rev isch
Med Rx
E S T Before and After RevascularizationClass I• 1. Demo of ischemia before revascularization.• 2. Eval rec symps suggesting ischemia aft revascularization.Class IIa• Aft discharge for activity counseling and/or exercise training as part of
rehabilitation in pts aft revascularization.Class IIb• 1. Detection of restenosis in selected, high-risk asymptomatic pts < first
12 months aft PCI.• 2. Periodic monitoring of selected, high-risk asymptomatic ps for
restenosis, graft occlusion, incomplete coronary revascularization, or disease progression.
Class III• 1. Localization of ischemia for determining the site of intervention.• 2. Routine, periodic monitoring of asymptomatic pts after PCI or CABG
without specific indications.
Investigation of Heart Rhythm Disorders
Class I• 1. Identification of appropriate settings in pts
with rate-adaptive pacemakers.• 2. Evaluation of cong CHB in pts considering
↑activity/competitive sports. (C)Class IIa• 1. Evaluating known or suspected exercise-
induced arrhythmias.• 2. Evaluation of medical, surgical, or ablative
therapy in exercise-induced arrhythmias
Investigation of Heart Rhythm Disorders
Class IIb• 1. Isolated VPC in middle-aged pts without
other evidence of CAD.• 2. Prolonged 1˚AV block or type I-2˚AV block ,
LBBB, RBBB, or VPC in young pts considering competitive sports. (C)
Class III• Routine investigation of isolated VPC in
young pts.
IN VALVULAR HEART DISEASE• Class1- c/c AR-Fun capacity & symp resp in
pats with equivocal sympt
• Class 2A c/c AR- FN capacity- athletic activity prog in c/c AR before AVR
Stress Testing
Modality Sensitivity Specificity
Exercise test 68% 77%
Nuclear Imaging 87-92% 80-85%
Stress Echo
80-85% 88-95%
EST RESPONSES & INTERPRETATIONS
Normal Response to Stress Testing• Heart rate increases
• Blood pressure increases
• Cardiac output increases
• Total peripheral resistance decreases
• Dysrhythmias – isolated unifocal PVC’s and PAC’s (suppressed at increased heart rate)
• Oxygen consumption increases
Abnormal Response to Stress Testing
• Heart rate fails to rise above 120 or unable to attain THR of 85% of max
• SBP shows a drop
• Physically unable to complete test
• Marked hypertension, >260/115
• Chest Pain and/or unusual shortness of breath
Normal Response of ECG to Stress Testing
• ECG Changes
– QRS complex ↓ in size– PR,QRS,QT shorten– J point ↓, resulting in up sloping of ST segment– ST segment returns to baseline by 80
milliseconds– PR segment may down slope(Inf leads– baseline
PQ junction)– R amplitude may decr at rates > 130– P ampl ↑– T wave decreases
The Electrocardiographic Response
1 = Iso-electric2 = J point3 = J + 80 msec
The Exercise ECG
• ST 60 -- HR > 130/min
• ST 80 -- HR ≤ 130/min
Criteria for Reading ST-Segment Changes on the Exercise ECG
ST DEPRESSION:
• Measurements made on 3 consecutive ECG complexes
• ST level is meas rel to the P-Q junction
• When J-point is dep rel to P-Q junction at baseline:
– Net diff from the rest J junction - amount of deviation
• When the J-point is ↑ rel to P-Q junction at baseline and becomes ↓ isoel with exercise:
– Mag of ST dep - P-Q junction and not the resting J point
Abnormal and Borderline ST-Segment Depression
• ABNORMAL:– 1.0 mm or > horizontal or downsloping ST dep at
80 msec after J point on 3 consecutive ECG complexes
• BORDERLINE:– 0.5 to 1.0 mm horizontal or downsloping ST dep at
80 msec after J point on 3 consecutive ECG complexes
– 1.5 mm or > upsloping ST dep at 80 msec after J
point on 3 consecutive ECG complexes
ECG changes during stress test
Normal
Rapid Upsloping
Minor ST Depression
Slow Upsloping
Horizontal
Downsloping
Elevation (non Q lead)
Elevation (Q wave lead)
ECG Patterns Indicative of Myocardial Ischaemia
ECG Patterns Not Indicative of Myocardial Ischaemia
• In lead V4 , the exercise ECG result is abnormal early in the test, reaching 0.3 mV (3 mm) of horizontal ST segment depression at the end of exercise.
• severe ischemic response.
•The J point at peak exertion is depressed 2.5 mm, the ST segment slope is 1.5 mV/sec, and the ST segment level at 80 msec after the J point is depressed 1.6 mm.
• “slow upsloping” ST segment at peak exercise indicates an ischemic pattern in patients with a high coronary disease prevalence pretest.
•typical ischemic pattern is seen at 3 minutes of the recovery phase when the ST segment is horizontal and 5 minutes after exertion when the ST segment is downsloping.
• abnormal at 9:30 minutes ES test and resolves in the immediate recovery phase.
•pattern in which the ST segment becomes abnormal only at high exercise workloads and returns to baseline in the immediate recovery phase may indicate a false-positive result in an asymptomatic individual without atherosclerotic risk factors.
ST ElevationAbnormal response
– J ↑ ≥0.10mV(1 mm)– ST 60 ≥0.10mV(1 mm)– Three consecutive beats
Q wave lead (Past MI)• Severe RWMA, ↓EF, ↓PrognosisNon Q wave lead (Past MI)• Severe ischemic response• Localise the culpritNon Q wave lead (No past MI)-1%• Transmural reversible myocardial ischemia-
----vasospasm, ↑coronary narrowing
•ST segment elevation in leads V2 and V3 with lesser degrees of ST segment elevation in leads V1 and V4 and J point depression with upsloping ST segments in lead II, associated with angina
•pattern is usually associated with a full-thickness, reversible myocardial perfusion defect in the corresponding left ventricular myocardial segments and high-grade intraluminal narrowing at coronary angiography
• coronary vasospasm produces this result in the absence of significant intraluminal atherosclerotic narrowing
Confounders of EST Interpretation• Digoxin
– abnormal ST-segment response to exercise.– occurs in 25% to 40% – directly related to age.
• LVH
– ↓ specificity of EST, sensitivity unaffected. – still the first test – Ab test- ref to add tests
• Resting ST ↓
– Resting ST-segment ↓ -even otherwise adverse
• LBBB– Ex-induced ST ↓ -no asso with ischemia
– no level of ST-seg dep - diag
• RBBB– do not ↓ sensitivity, specificity, or predictive value
• β- # THERAPY
– routine- unnecessary- to stop beta-blockers-† symp
– in patients taking -↓ diag & prog value - inadequate HRR
ERS and resting ST↑
• Return to the PQ Jn –nl
• ST↓ meas from PQ jn
• Not from the elevated J point before ex.
Duke Treadmill Score
Treadmill Score =
Ex.tme (min)
-5х (ST-seg dev in mm)- 4х ex.angina index
(0-no angina, 1 angina, 2 if angina stops test)
High Risk= -11, mortality - >5% annually
Low Risk= +5, mortality - 0.5% annually
DUKE TM SCORE
• Independent prog information
• =y good in males & females
• Not as effective in age≥ 75 yrs
ACC/AHA Guidelines:
high-risk test result- mortality ≥ 4%/yr→ for
cardiac cath
Intermediate-risk result -mortality 2- 3%/yr→
additional testing- cardiac cath, exercise
imaging study
Pseudo normalization pattern of T
• No prior MI Nondiagnostic finding
• Prior MI Sugg Reversible myocardial ischemia Needs - rev myo perfusion defect
R Wave amplitudeLVH Voltage criteria• ST seg – less reliable to ∆ CAD even in the
absence of LV strain pattern
Loss of R wave (MI)• ↓Sensitivity of ST response in that lead
U inversion
Occ in precordial leads at HR<120• Relatively insensitive but • Relatively specific 4 CAD
ST/HR SLOPE MAESUREMENTS• HR adj of ST seg dep-↑ sensitivity
• ST/HR slope of 2.4 mV/beats/min-abnormal
• >6mV/beats/min -3 vessel disease
• CORNELL protocol-gradual inc in HR
• ST seg/HR index-av change of ST dep with HR through out the course of ex test
• > 1.6 -abnormal
Abnormal BP Response• Failure to ↑SBP >120 mmHg
• Sustained ↓(15 secs) >10mmHg
• ↓SBP below resting BP during progressive exe• Inadequate ↑ of CO
• Hypo episode 3- 9% of symp pats Extensive CAD & perfusion defects LMCA/ 3 VD
Exercise CapacityVO max = (mph x 26.8) x (0.1 + [% grade X 1.8] + 3.5
Stage 1 = 5 METS
Stage 2 = 6 - 8 METS
Stage 3 = 8 -10 METS
2
2
1-MET ↑in exercise capacity, the survival improved by 12 % N Engl J Med 2002
Heart rate response Chronotropic incompetence-adv prog• Inability to attain THR OR• Ab HRR (<80%)
{%HR Reserve=(HRpeak-HRrest)/(220-age- HRrest)} Chronotropic index• ANS dysfunction,SN dysfuntion, drugs,
myocardial ischemia• ↑long term mortality-< 80%CI (not on β
blockers)
Heart Rate Recovery
-Rapid reactivation of vagal tone - ↓ in heart rate post ex- nl
-Slow decceleration post ex
-↓ vagal tone
HRR=HR (peak)-HR (1 min later)
TMT (upright) < 12 bpm
TMT (supine) < 18 bpm
upright value <22 bpm at 2 minutes is abnormal
Prognostic power independent of other factors
HRR Predicts Outcome in CAD
Exercise induced Chest discomfort• Usually after ischemic ST changes• +/-↑DBP• chest discomfort –only sgn of CAD
• In CSA, CP less freq than ST↓Angina with no ST ↓- MPI to assess ischemic
severity.
(+) Stress Test with angina → 5%/yr.( mortality)
(+) Stress Test, no angina → 2.5%/yr.
Adverse prognosis & multivessel CAD• Symptom limiting exercise < 5METs
• Abnormal BP response
• ST↓ ≥2mm or downsloping ST↓→ <5METs, ≥5 leads, persisting ≥5 mins into recovery
• ST↑( except aVR)
• Angina at low exercise work loads
• Reproducible sustained/symptomatic VT
Indications for Terminating Exercise Testing
Absolute indications• ↓ SBP >10 mm Hg fm baseline +other evidence of
ischemia• Mod - severe angina• ↑ CNS sympts (ataxia, dizziness, or near-syncope)• Signs of poor perfusion (cyanosis or pallor)• Technical diff in monitoring ECG or systolic BP• Subject’s desire to stop• Sustained VT• ST ↑ (≥1.0 mm) in leads without Q-waves (other
than V1 or aVR)
Relative indications• ↓ in S BP (≥10 mm Hg) in the absence of other
evidence of ischemia• ST or QRS changes - excessive ST↓ (>2 mm of
horizontal or downsloping ST↓ ) or marked axis shift• Arrhythmias other than sustained VT, including
multifocal PVCs, triplets of PVCs, SVT, heart block, or bradyarrhythmias
• Fatigue, shortness of breath, wheezing, leg cramps, or claudication
• Devp of BBB or IVCD that cannot be distinguished from VT
• Increasing chest pain• Hypertensive response(250/115 mm hg)
Sub maximal ex test• Signs & sympt of ischemia
• Att of a work load of 6 METS
• 85% of APMHR
• HR of 110 beats / min –on β blockers
• BORG score 17
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